The skeletal muscle plays a key role in systemic energy homeostasis besides its canonical contractile function, but what couples these functions is poorly defined. Protein Arginine MethylTransferase 5 (PRMT5) is a well-known oncoprotein but also expressed in healthy tissues with unclear physiological functions. As adult muscles express high levels of Prmt5, we generated myocyte-specific Prmt5 knockout (Prmt5MKO) mice. We observed reduced muscle mass, oxidative capacity, force production and exercise performance in Prmt5MKO mice. The motor deficiency is associated with scarce lipid droplets in myofibers due to defects in lipid biosynthesis and degradation. First, Prmt5MKO reduced demethylation and stability of Sterol Regulatory Element-Binding Transcription Factor 1a (SREBP1a), a master regulator of de novo lipogenesis. Second, Prmt5MKO impaired the repressive H4R3Me2s (histone H4 arginine-3 symmetric demethylation) at the Pnpla2 gene, elevating the level of its encoded protein ATGL, the rate-limiting enzyme catalyzing lipolysis. Accordingly, myocyte-specific double knockout of Pnpla2 and Prmt5 normalized muscle mass and function. Together, our findings delineate a physiological function of PRMT5 in linking lipid metabolism to contractile function of myofibers.